RESUMO
Some types of plant accumulate liquid in their inflorescences creating phytotelmata. These environments protect the flowers against florivory, although they may be colonized by aquatic or semi-aquatic florivorous insect larvae, whose effects on the fitness of the plants remain unclear. We tested the hypothesis of floral antagonism by the occupants of phytotelmata, which predicts that florivory by the occupants of the phytotelmata represents a cost to the female fitness of the plant, reducing its fecundity. We manipulated experimentally the infestation by 3 florivores larvae species occupants of phytotelmata in inflorescences of Heliconia spathocircinata (Heliconiaceae) to test for negative direct trophic effects on the fecundity of the flowering and fruiting bracts. We found that the foraging of the hoverfly (Syrphidae) and moth (Lepidoptera) larvae in the inflorescences contributed to a decline in the fecundity of the plant. While the lepidopteran impacted fecundity when foraging in both flowering and fruiting bracts, the syrphid only affected the fruiting bracts, which indicates that the nectar and floral tissue are the principal resource exploited by the hoverfly. By contrast, soldier fly (Stratiomyidae) had a neutral effect on fecundity, while foraging in flowering or fruiting bracts. These findings corroborate our hypothesis, that herbivory by the larval occupants represents cost to the host plant having phytotelmata. The negative influence of this foraging on plant fecundity will nevertheless depend on the consequences of the exploitation of resources, which vary considerably in ephemeral habitats such as the phytotalmanta of flower parts.
RESUMO
Restinga occurs as a narrow band of coastal habitats throughout the Atlantic Forest, although it presents considerable variation in vegetation structure, which likely contributes to heterogeneity in species inhabiting this endangered ecosystem. The goal of this study is to examine how variation in vegetation and abiotic conditions in the restinga ecosystem may contribute to heterogeneity of bird communities in Restinga de Jurubatiba, Brazil. Temperature, relative humidity, and vegetation structure were sampled to characterize four sites (dry forest, flooded forest, open scrub and closed scrub). Birds were sampled using observations, mist-netting and voice recordings. Results indicate that major differences of all variables occur between forest and scrub in both vegetation and birds. In addition, differences also exist within forests and within scrub, resulting in considerable heterogeneity among sampled areas. Scrub sites were richer in bird species (n = 58) than forest sites (n = 41), while closed scrub had the most species (n = 49). Also, 64% (47 of 73) of bird species were exclusive to forest or scrub habitats. Scrub habitats were more similar to each other than forest habitats. Normalized Difference Vegetation Index (NDVI) calculated from satellite images distinguished scrub sites and may be useful to monitor changes in vegetation patches through time. The restinga ecosystem is quite heterogeneous with considerable turnover in bird species composition and differences in vegetation structure. Forest strips may serve as connectors on the landscape and to help maintain species diversity and conservation of forest species. Also, this highly dynamic ecosystem, which includes a mosaic of habitat types, likely promotes resilience of bird populations under changing conditions.(AU)
Assuntos
Animais , Áreas Alagadas/efeitos adversos , Biodiversidade , Ecossistema , Aves/classificação , Áreas Alagadas/análise , Grupos de População Animal , FlorestasRESUMO
Restinga occurs as a narrow band of coastal habitats throughout the Atlantic Forest, although it presents considerable variation in vegetation structure, which likely contributes to heterogeneity in species inhabiting this endangered ecosystem. The goal of this study is to examine how variation in vegetation and abiotic conditions in the restinga ecosystem may contribute to heterogeneity of bird communities in Restinga de Jurubatiba, Brazil. Temperature, relative humidity, and vegetation structure were sampled to characterize four sites (dry forest, flooded forest, open scrub and closed scrub). Birds were sampled using observations, mist-netting and voice recordings. Results indicate that major differences of all variables occur between forest and scrub in both vegetation and birds. In addition, differences also exist within forests and within scrub, resulting in considerable heterogeneity among sampled areas. Scrub sites were richer in bird species (n = 58) than forest sites (n = 41), while closed scrub had the most species (n = 49). Also, 64% (47 of 73) of bird species were exclusive to forest or scrub habitats. Scrub habitats were more similar to each other than forest habitats. Normalized Difference Vegetation Index (NDVI) calculated from satellite images distinguished scrub sites and may be useful to monitor changes in vegetation patches through time. The restinga ecosystem is quite heterogeneous with considerable turnover in bird species composition and differences in vegetation structure. Forest strips may serve as connectors on the landscape and to help maintain species diversity and conservation of forest species. Also, this highly dynamic ecosystem, which includes a mosaic of habitat types, likely promotes resilience of bird populations under changing conditions.
Assuntos
Animais , Aves/classificação , Biodiversidade , Ecossistema , Áreas Alagadas/análise , Áreas Alagadas/efeitos adversos , Florestas , Grupos de População AnimalRESUMO
Legitimate flowers visitors pollinate the flower during the visit and thus influence the production of fruits and seeds. We tested whether the visitation rate of potential pollinators is associated with the amount of seeds per fruit produced by the self-compatible bromeliad Tillandsia stricta (Bromeliaceae). We determined whether hummingbirds are legitimate visitors by testing for a correlation between visits and pollination (seed production) at the Guapiaçú Ecological Reserve (Reserva Ecológica de Guapiaçú), state of Rio de Janeiro. We tested 30 flowers, five of which were also monitored to test the possibility of spontaneous self-pollination. The remaining 25 flowers were exposed to floral visitors. Twenty-two flowers formed fruits and seeds, from which three formed seeds without floral visits. The hummingbird Amazilia fimbriata (Gmelin, 1788) was the only legitimate visitor. The average number (± standard deviation) of seeds was 27 units (±15) per fruit. The floral visitation rate by A. fimbriata was 6.6 (±3.4) visits/per flower. The number of floral visits and the amount of seed produced were positively correlated (r² = 0.58, p 0.01). Thus, A. fimbriata is a legitimate floral visitor of T. stricta, and influences seed production per fruit in this bromeliad.(AU)
Assuntos
Tillandsia/crescimento & desenvolvimento , PolinizaçãoRESUMO
Legitimate flowers visitors pollinate the flower during the visit and thus influence the production of fruits and seeds. We tested whether the visitation rate of potential pollinators is associated with the amount of seeds per fruit produced by the self-compatible bromeliad Tillandsia stricta (Bromeliaceae). We determined whether hummingbirds are legitimate visitors by testing for a correlation between visits and pollination (seed production) at the Guapiaçú Ecological Reserve (Reserva Ecológica de Guapiaçú), state of Rio de Janeiro. We tested 30 flowers, five of which were also monitored to test the possibility of spontaneous self-pollination. The remaining 25 flowers were exposed to floral visitors. Twenty-two flowers formed fruits and seeds, from which three formed seeds without floral visits. The hummingbird Amazilia fimbriata (Gmelin, 1788) was the only legitimate visitor. The average number (± standard deviation) of seeds was 27 units (±15) per fruit. The floral visitation rate by A. fimbriata was 6.6 (±3.4) visits/per flower. The number of floral visits and the amount of seed produced were positively correlated (r² = 0.58, p 0.01). Thus, A. fimbriata is a legitimate floral visitor of T. stricta, and influences seed production per fruit in this bromeliad.
Assuntos
Polinização , Tillandsia/crescimento & desenvolvimentoRESUMO
The purpose of this study was to investigate the reproductive phenology and sharing of floral resource (nectar) of Dahlstedtia pinnata (Benth.) Malme. (Fabaceae), endemic of Atlantic forest, among hummingbirds. For the phenology, we looked at the presence of reproductive structures in the plants, and for floral resource sharing, the frequency of potential pollinators and foraging behaviors were examined. This study was conducted in Pedra Branca State Park, in state of Rio de Janeiro, in a dense ombrophilous forest, between August 2010 and August 2011. Flowering occurred between December 2010 and March 2011, and fruiting between April and June 2011. Hummingbirds' foraging schedules differed significantly, with legitimate visits to the flowers occurring in the morning and illegitimate visits occurring during late morning and the afternoon. Five species visited flowers, three of which were legitimate visitors: Phaethornis ruber, P. pretrei, and Ramphodon naevius. Amazilia fimbriata and Thalurania glaucopis females only visited illegitimately. Phaethornis ruber robbed nectar (78% of illegitimate visits, n=337). Ramphodon naevius, with a territorial foraging behavior and a body size bigger than that of other observed hummingbird species, dominated the floral visits, which suggests that D. pinnata is an important nourishing resource for this endemic bird of the Atlantic forest, currently globally categorized as Near Threatened.